[Solved] Find the issue in this query:SELECT user_id, score, LEAD(score) OVER () AS next_score FROM scores ORDER BY user_id; | PostgreSQL

PostgreSQL - Window Functions in PostgreSQL

Find the issue in this query:

SELECT user_id, score, LEAD(score) OVER () AS next_score FROM scores ORDER BY user_id;

ALEAD cannot be used with ORDER BY clause

BLEAD requires a partition clause

CMissing ORDER BY inside OVER() causes undefined row order

DQuery will return syntax error

Step-by-Step Solution

Solution:

Step 1: Understand OVER() usage
LEAD without ORDER BY inside OVER() means no defined row order for lead calculation.
Step 2: Check query behavior
ORDER BY outside OVER() sorts final output but does not define row order for LEAD, causing unpredictable results.
Final Answer:
Missing ORDER BY inside OVER() causes undefined row order -> Option C
Quick Check:
LEAD needs ORDER BY inside OVER() for correct next row [OK]

Quick Trick: ORDER BY inside OVER() defines row order for LAG/LEAD [OK]

Common Mistakes:

Master "Window Functions in PostgreSQL" in PostgreSQL

9 interactive learning modes - each teaches the same concept differently

Find the issue in this query: